Catalyst compositions for preparing polyorganosiloxanes

ABSTRACT

Polyorganosiloxanes are prepared from at least one organosiloxane reactant containing an average of more than one silicon-bonded hydroxyl group per molecule using novel catalyst compositions consisting essentially of (1) at least one salt formed from equimolar amounts of an amine and sulfuric acid, phosphoric acid, a carboxylic acid or an organosulfonic acid and (2) an unreacted acid selected from the group consisting of sulfuric acid and fluorinated alkanesulfonic acids.

This application is a division of application Ser. No. 519,357, filed8/1/83.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preparation of polyorganosiloxanes. Moreparticularly, this invention relates to a method and certain novelcatalyst compositions for preparing polyorganosiloxanes from one or moreorganosiloxanes containing silicon-bonded hydroxyl groups.

2. Description of the Prior Art

Polyorganosiloxanes are well known materials, and range in consistencyfrom liquids to resinous or elastomeric solids at room temperature. Thephysical state of a given polyorganosiloxane is a function of itsmolecular weight and the type and number of hydrocarbon groups bonded tosilicon.

Polyorganosiloxanes have been prepared by a variety of methods. Inaccordance with one such method, one or more silanes or siloxanescontaining silicon-bonded hydroxyl groups are reacted in the presence ofsuitable condensation catalysts. U.S. Pat. No. 3,308,203, which issuedto Metevia and Polmanteer on Mar. 7, 1967, discloses several classes ofcompounds that catalyze the condensation of silicon-bonded hydroxylgroups. Among the classes of catalysts disclosed are alkali metalhydroxides, organosilicon salts of alkali metal hydroxides, primary,secondary and tertiary amines, aromatic sulfonic acids,fluoroalkanesulfonic acids, and salts obtained by the reaction of "basicamino compounds" with either phosphoric acid or carboxylic acids. Theaforementioned patent teaches that these catalysts do not causeexcessive siloxane bond rearrangement, and are therefore useful forpreparing organosiloxane block copolymers.

Applicant has found that some of the preferred catalysts exemplified inthe aforementioned patent either will not produce polyorganosiloxanes ofsufficiently high molecular weight to yield elastomers and resins havingcommercially useful physical properties, or the catalysts must be usedin such large concentrations that they adversely affect the physical orchemical properties of the final cured polyorganosiloxane.

An additional problem associated with using many prior art catalysts isthat in addition to accelerating the reaction between two silicon-bondedhydroxyl groups to form ═SiOSi═ bonds, at the required use levels thecatalysts may accelerate a hydrolysis of previously formedsilicon-oxygen bonds. This can result in the formation of cyclicorganosiloxane oligomers and a reduction in the average molecular weightof the polymer. The cyclic organosiloxanes typically have relatively lowboiling points and are readily distilled from the reaction mixturetogether with the liquid hydrocarbon often employed as a reactionmedium. The formation of cyclic organosiloxanes place an upper limit onthe average molecular weight that can be achieved under a given set ofconditions. In addition, the rearrangement and equilibration of siloxanebonds could destroy the alternating sequences of repeating units thatcharacterize the structure of block copolymers.

An objective of this invention is to provide a method and novel catalystcompositions for preparing high molecular weight polyorganosiloxanes,including block copolymers, by a condensation reaction between one ormore hydroxyl-containing polyorganosiloxanes. An additional objective isto provide novel catalysts for the reaction between silicon-bondedhydroxyl groups that are effective at concentration levels which do notadversely affect electrical and other properties of the resultantpolymer.

SUMMARY OF THE INVENTION

The foregoing objectives and others can be achieved by the presentmethod for preparing polyorganosiloxanes, which comprises reacting oneor more hydroxyl-containing organosiloxanes in the presence of an inertliquid reaction medium and a catalytically effective amount of a novelcatalyst composition consisting essentially of an acid selected fromsulfuric acid and fluorinated alkanesulfonic acids, and a salt derivedfrom an organic amine containing at least one primary, secondary ortertiary nitrogen atom and an acid selected from the group consisting ofcarboxylic acids, sulfuric acid, organosulfonic acids, and phosphoricacid.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a method for preparing a polyorganosiloxane, saidmethod comprising the steps of (I) forming a liquid reaction mixturecomprising (A) at least one hydroxyl-containing organosiloxane reactantcontaining repeating units of the formula R_(a) ¹ SiO_(4-a) where eachR¹ is individually selected from the group consisting of monovalentinertly substituted and monovalent unsubstituted hydrocarbon radicalscontaining from 1 to 6 carbon atoms and a has an average value of from 1to 2; (B) a catalytically effective amount of a catalyst compositionconsisting essentially of (1) at least one salt derived fromsubstantially equivalent amounts of an organic mono- or polyfunctionalamine and an acid selected from the group consisting of mono- andpolyfunctional carboxylic acids, mono- and polyfunctional organosulfonicacids, phosphoric acid and sulfuric acid, and (2) at least one unreactedacid selected from the group consisting of fluorinated alkanesulfonicacids and sulfuric acid, and (C) an inert liquid reaction medium; (II)heating said reaction mixture at a temperature of from 30° C. to theboiling point of the reaction mixture while removing the by-producedwater from the reaction mixture; and (III) maintaining said temperaturefor a period of time sufficient to form said polyorganosiloxane.

In a preferred embodiment of this invention, the polyorganosiloxane is ablock copolymer prepared by reacting (i) a hydroxyl-terminatedpolydiorganosiloxane having repeating units of the general formula R² R³SiO, where R² and R³ are individually selected from the same group asR¹, with (ii) an organosiloxane containing units of the formula ##EQU1##where R⁴ is selected from the group defined hereinbefore for R¹, withthe proviso that R², R³ and R⁴ are not identical when b is 2; R⁵ isalkyl containing from 1 to 4 carbon atoms; b has an average value offrom 1 to 2, inclusive; c is at least 0.01; d has an average value offrom 0 to 1.5, the sum of b, c and d does not exceed 3; and the molarratio of R² R³ SiO units to ##EQU2## is from 0.1:1 to 10:1,respectively.

This invention also provides novel catalyst compositions for preparingpolyorganosiloxanes by the condensation reaction of at least oneorganosiloxane containing an average of more than one silicon-bondedhydroxyl group per molecule. The catalyst compositions contain at leastone each of the salts and unreacted acids previously defined herein inconnection with the method of this invention.

The catalyst compositions employed in accordance with the present methodmake it possible to reproducibly prepare polyorganosiloxanes exhibitingcommercially useful levels of physical properties such as tensilestrength and elongation. An additional advantage of the present catalystcompositions is that they can be employed at sufficiently smallconcentrations which do not adversely affect the electrical and otherproperties of the final block copolymer. Preferred catalyst compositionswill not excessively corrode metal reactors and associated processingequipment.

The amine salt component (1) of the present catalyst compositions is thereaction product of an organic amine containing at least one primary,secondary or tertiary nitrogen atom with a substantially equivalentamount of a carboxylic acid, an organosulfonic acid, sulfuric acid, orphosphoric acid. As defined for purposes of the present invention,organic amines contain no active hydrogen atoms other than those formingpart of the amine group, and the term "equivalent amount" refers to thatamount of acid sufficient to react with all of the amino groups withoutany excess sulfuric acid, phosphoric acid, --COOH or --SO₃ H groupsbeing present in the reaction product.

Specific examples of suitable amines include aliphatic primary,secondary and tertiary amines such as methylamine, diethylamine,n-propylamine, tri-n-propylamine, di-iso-propylamine, n-butylamine,t-butylamine and di-n-octylamine; cycloaliphatic amines such ascyclohexylamine; aromatic amines such as aniline and heterocyclic aminessuch as pyridine and pyrrole. Suitable polyfunctional amines includeethylenediamine, diethylenetriamine, pyrimidine, guanidine, andN-alkylated guanidines. Preferably, the amine is either a monoalkylaminecontaining from 1 to 8 carbon atoms, most preferably t-butylamine, or a1,1,3,3-tetraalkylguanidine wherein the alkyl radicals of the aminecontain from 1 to 8 carbon atoms. Most preferably thetetraalkylguanidine is 1,1,3,3-tetramethylguanidine, hereinafterreferred to as tetramethylguanidine. The preference for certain aminesis based on their availability and the properties of polymers preparedusing salts of these amines.

The acid employed to prepare the amine salt can be sulfuric acid,phosphoric acid, a mono- or polyfunctional carboxylic acid or a mono- orpolyfunctional organosulfonic acid. The hydrocarbon portion of thecarboxylic or organosulfonic acid can be unsubstituted or inertlysubstituted, and contains from 1 to 20 or more carbon atoms. Thesubstituents that can be present include alkoxy groups and halogenatoms. Examples of suitable carboxylic acids include acetic,methoxyacetic, trifluoroacetic, propionic, butyric, n-hexanoic, adipic,2-ethylhexanoic, octanoic, suberic, decanoic, stearic, oleic, benzoic,p-chlorobenzoic, benzoic and the isomeric phthalic acids. Examples ofsuitable organosulfonic acids are methanesulfonic, ethanesulfonic,n-butanesulfonic, benzenesulfonic and p-toluenesulfonic acids. Preferredacids include sulfuric acid and carboxylic and organosulfonic acidscontaining at least one halogen atom on the hydrocarbon radical. Thehalogen is most preferably fluorine and is present as a polyfluorinatedalkyl radical. Preferred fluorine-containing acids includetrifluoroacetic acid, trifluoromethanesulfonic acid, andtetrafluoroethanesulfonic acid. Fluorinated sulfonic acids are mostpreferred based on the small salt concentrations required and theproperties of polyorganosiloxanes obtained using salts of these acids ascatalysts.

Methods for preparing salts by the reaction of an organic amine with anequivalent amount of a suitable carboxylic acid, organosulfonic acid,sulfuric acid, or phosphoric acid are thoroughly discussed in thechemical literature, and are not part of this invention.

The salt component (1) of the present catalyst compositions is typicallyemployed at a concentration of from about 10 to about 500 parts byweight per million parts (ppm) of total organosiloxane reactants. Theoptimum concentration range for a given salt is a function of severalfactors, including the catalytic activity of the salt, its thermalstability and the boiling points of the amine and acid components of thesalt. It is therefore not feasible to define preferred concentrationlimits for every operable salt, however these can be readily determinedwith a minimum of experimentation.

The preferred sulfuric, trifluoroacetic, and trifluoromethanesulfonicacid salts of lower N-alkyl amines, such as t-butyl amine andtetramethylguanidine, are employed at concentration levels of from 50 to200 ppm.

In some instances it may be necessary to add one or both of the acid andamine portions of the salt during the polymerization reaction to replacematerial lost by decomposition of the salt and subsequent distillationof the acid and/or amine portion of the salt together with the waterformed as a by-product of the reaction.

The presence of sufficient catalyst during the polymerization canreadily be determined by periodically determining the molecular weightof the polymer using any of the known techniques, including viscositymeasurement, gel permeation chromatography and osmometry.

In addition to the aforementioned salt (1), the present catalystcompositions also contain an unreacted acid component (2), that iseither sulfuric acid or a fluoroalkanesulfonic acid. Preferably thefluoroalkanesulfonic acid is represented by the formula R_(f) SO₃ Hwhere R_(f) represents a perfluoroalkyl radical containing from 1 to 12carbon atoms, a H(CF₂)_(d) CF₂ -- radical, or a F(CF₂)_(d) CFHCF₂ --radical and d is 0, 1 or 2. Fluoroalkanesulfonic acids corresponding tothese formulae include CF₃ SO₃ H, C₂ F₅ SO₃ H, C₄ F₉ SO₃ H, C₈ F₁₇ SO₃H, HCF₂ CF₂ SO₃ H, CF₂ HSO₃ H and CF₃ CFHCF₂ SO₃ H. Preferably R_(f)represents a lower perfluoroalkyl group, most preferablytrifluoromethyl, or R_(f) represents HF₂ CCF₂ --. The unreacted acid ispresent at a concentration which is catalytically effective for thecondensation of silicon-bonded hydroxyl groups. Typically, thefluoroalkanesulfonic acid or sulfuric acid is present at concentrationsof from 10 to 300 ppm.

In some instances the unreacted acid appears to catalyze a hydrolysis ofsilicon-oxygen bonds to form lower molecular weight, hydroxyl-terminatedpolyorganosiloxanes. For example, when preparing block copolymers from apolydimethylsiloxane and hydrolyzed phenyltrimethoxysilane, it has beenfound that the dimethylsiloxane portions of the final copolymer are ofequivalent molecular weights, irrespective of the molecular weight ofthe initial polydimethylsiloxane used to prepare the copolymer. It hasalso been found that copolymers can be prepared usingtrimethylsiloxy-endblocked polydimethylsiloxanes as one of the tworeactants. This indicates that some hydrolysis to formhydroxyl-containing reactants is occurring concurrently with copolymerformation.

Surprisingly, the aforementioned hydrolysis does not affect thephenylsiloxane portion of the copolymer, nor does it appear to adverselyaffect the ordered structure of the final block copolymer, as evidencedby the physical properties of the cured copolymer.

The weight ratio of amine salt component to unreacted acid component ofthe present catalyst compositions is from 1:30 to 50:1, respectively.Preferably this ratio is from 1:3 to 3:1.

The organosiloxane reactants employed to prepare polyorganosiloxanes inaccordance with the present method contain an average of more than one,preferably two or more silicon-bonded hydroxyl groups per molecule. Whenthe final polyorganosiloxane is a homopolymer, the organosiloxanereactant preferably contains an average of at least 1.8 silicon-bondedhydroxyl groups per molecule.

The organosiloxane reactants are typically low molecular weight,hydroxylated polyorganosiloxanes containing an average of two or morerepeating siloxane units per molecule than can be represented by theaforementioned general formula R_(a) ¹ SiO.sub.(4-a)/2 where each R¹ isindividually selected from the group consisting of monovalent inertlysubstituted and monovalent unsubstituted hydrocarbon radicals containingfrom 1 to 6 carbon atoms and a has an average value of from 1 to 2.

Representative unsubstituted monovalent hydrocarbon radicals includealkyl such as methyl, ethyl, propyl, butyl, and hexyl; alkenyl such asvinyl; cycloalkyl such as cyclohexyl; and aryl such as phenyl. When R¹represents an acyclic hydrocarbon radical it can be linear or branched.When R¹ represents an inertly substituted hydrocarbon radical, thesubstituent can be, for example, halogen, alkoxy or cyano. Thesesubstituents are considered inert, in that they do not react under theconditions employed to polymerize the siloxane reactants.

Preferably R¹ represents methyl, phenyl or 3,3,3-trifluoropropyl. Thispreference is based on the availability of intermediates employed toprepare the siloxane reactants.

As disclosed hereinbefore, a hydroxyl-containing diorganosiloxanereactant can be formed in situ during the polymerization reaction from atrihydrocarbylsiloxy-endblocked polydiorganosiloxane and sufficientwater to hydrolyze a portion of the silicon-oxygen bonds of thepolydiorganosiloxane.

Preferred siloxane reactants for preparing homopolymers include lowmolecular weight hydroxyl-terminated polydiorganosiloxanes containing anaverage of from 10 to about 100 repeating units per molecule. In theseembodiments R_(a) ¹ SiO.sub.(4-a)/2 represents a dimethylsiloxane,methylvinylsiloxane, methylphenylsiloxane or amethyl-3,3,3-trifluoropropylsiloxane unit. Other preferredhydroxyl-containing polymers and oligomers contain from 10 to about 100monoorganosiloxane units per molecule of the formula RSiO_(3/2) where Rrepresents an inertly substituted or an unsubstituted hydrocarbonradical as defined hereinbefore for R¹. Homopolymers prepared from thesemonoorganosiloxane reactants are typically resinous materials.

Copolymers can be prepared using the present catalyst compositions byreacting two or more organosiloxane reactants. To obtain commerciallyuseful products at least two of the reactants should contain an averageof two or more silicon-bonded hydroxyl groups per molecule. Theparticular organosiloxane reactants selected and their relativeconcentrations will determine the physical properties of the finalcopolymer.

The present catalyst compositions are particularly useful for preparingblock copolymers by reacting at least one hydroxyl-terminatedpolydiorganosiloxane (i) containing repeating units of the formula R² R³SiO with at least one organosiloxane reactant (ii) containing repeatingunits of the average formula ##EQU3## The definitions for R², R³, R⁴,R⁵, b, c, and d appear hereinbefore.

Preferably at least 50 mol %, most preferably from 80 to 100 mol % ofthe hydrocarbon radicals represented by R² and R³ are methyl. Thispreference is based on the availability of the intermediates used toprepare polydiorganosiloxane (i) and the physical properties of blockcopolymers containing a diorganosiloxane block having at least 50 mol %of dimethylsiloxane units. Preferred copolymers containmethylphenylsiloxane and/or methyl-3,3,3-trifluoropropylsiloxane unitsin addition to dimethylsiloxane units. Most preferablypolydiorganosiloxane (i) is a polydimethylsiloxane.

Polydiorganosiloxane (i) can be a single species, such as the preferredpolydimethylsiloxane. Alternatively, polysiloxane (i) can be a mixtureof two or more polydiorganosiloxanes containing different R¹ and/or R²radicals, for example, a mixture of a polydimethylsiloxane and apolymethylphenylsiloxane.

Polydiorganosiloxane (i) may contain up to 2 mol % of monoorganosiloxaneunits. Typically these units result from impurities, usuallymonoorganotrihalosilanes, present in the diorganodihalosilanes used toprepare the polydiorganosiloxane.

Polydiorganosiloxane (i) typically contains an average of from 5 toabout 350 repeating units per molecule. When polydiorganosiloxane (i) isa polydimethylsiloxane, it preferably contains an average of from 10 to100 repeating units per molecule.

When R², R³, and R⁴ of polysiloxane (ii) represent the same hydrocarbonradical when b is 2 and only one type of polydiorganosiloxane is used aspolydiorganosiloxane (i), all of the blocks in the final "copolymer"would be identical, thereby making it a homopolymer.

Preferably at least half, most preferably all, of the radicalsrepresented by R⁴ are phenyl, R⁵ is methyl, and the average value of bin the preceding formula is from 1 to 1.3. These preferences are basedon the useful combination of physical properties achieved when thesepolymers are reacted with a polydiorganosiloxane (i) containing at least80 mol % of dimethylsiloxane units using the present catalystcompositions. Any radicals represented by R⁴ which are not phenyl arepreferably alkyl containing from 1 to 4 carbon atoms, vinyl, or3,3,3-trifluoropropyl.

Polyorganosiloxane (ii) preferably contains an average of from 0.1 to 1hydroxyl group per silicon atom, which is equivalent to a value for c inthe preceding formula of from 0.1 to 1.0.

Polyorganosiloxane (ii) may contain a combination of monoorganosiloxaneand diorganosiloxane units equivalent to an average value for b in thepreceding formula of from 1 to 1.9. Alternatively, polyorganosiloxane(ii) can be a hydroxyl-containing polydiorganosiloxane, in whichinstance b would have a value of 2. Typical diorganosiloxane groupswhich may be present include dimethylsiloxane, diphenylsiloxane,methyl-3,3,3-trifluoropropylsiloxane, methylvinylsiloxane, andmethylphenylsiloxane.

Preferred embodiments of polyorganosiloxane (ii), wherein the value of bis from 1 to 1.3, are conveniently prepared by hydrolyzing at least onemonoorganotrialkoxysilane, such as phenyltrimethoxysilane, alone or incombination with at least one diorganodialkoxysilane such asphenylmethyldimethoxysilane. To facilitate preparation of the blockcopolymer, at least 50%, preferably at least 80%, of the original numberof alkoxy groups are converted to hydroxyl groups or siloxane bonds,which is equivalent to a preferred value for d in the foregoing formulaof from 0 to 0.6.

The relative amounts of polydiorganosiloxane (i) and polyorganosiloxane(ii) employed to prepare preferred block copolymers are such that themolar ratio of diorganosiloxane units in polydiorganosiloxane (i) toorganosiloxane units in polyorganosiloxane (ii) is from 0.1:1 to 10:1,respectively. Preferably this ratio is from 0.7:1 to 3.5:1.

Organosiloxane homopolymers and copolymers are prepared in accordancewith the present method by reacting at least one hydroxyl-containingorganosiloxane reactant, as defined hereinabove, in the presence of atleast one amine salt component and at least one unreacted acid componentof the present catalyst compositions. The ranges for concentrations ofamine salt component and acid component of the catalyst composition withrespect to one another and with respect to the siloxane reactant(s) havebeen defined hereinbefore.

The organosiloxane reactant(s) and catalyst components are dissolved ordispersed in an inert liquid reaction medium having a boiling point offrom about 50° to about 150° C. under atmospheric pressure. The term"inert" implies that the reaction medium does not react or decomposeunder the conditions employed to polymerize the organosiloxanereactants. The reaction medium should be a solvent for the final polymerand the reactant(s) used to prepare it. Preferably the reaction mediumis a liquid aromatic hydrocarbon such as benzene, toluene or xylene thatforms an azeotropic mixture with the water generated as a by-product ofthe condensation reaction between silicon-bonded hydroxyl groups,thereby facilitating removal of the water from the reaction mixture.Removal of water and any alcohol formed by the hydrolysis ofsilicon-bonded alkoxy groups is usually a prerequisite for obtainingpolyorganosiloxanes of sufficiently high molecular weight to achievecommercially useful physical properties. The azeotropic mixturepreferably boils from 80° to 150° C. under atmospheric pressure.

Other suitable liquid reaction media include aliphatic hydrocarbons suchas hexane and halogenated hydrocarbons.

The amount of liquid reaction medium is not considered critical.Typically, the weight ratio of reaction medium to total organosiloxanereactants is from 1:1 to 3:1.

The mixture of organosiloxane reactant(s), catalyst composition andreaction medium is heated at a temperature of from 30° C. to the boilingpoint of the reaction mixture for a period of time required to produce apolyorganosiloxane of sufficient molecular weight that it exhibitsuseful properties following curing. Using toluene as the solvent,heating the reaction mixture at the boiling point for between 5 and 20hours will usually achieve this objective.

The course of a polymerization can conveniently be followed byperiodically measuring the molecular weight of the polyorganosiloxanebeing formed. Methods for determining molecular weight have beendiscussed hereinbefore. Typically, when a polydimethylsiloxane isreacted in a toluene reaction medium with a polyorganosiloxane whereinat least a major portion of the silicon atoms are bonded to phenylradicals and the solids concentration of the reaction mixture is equalto or exceeds 40% by weight, heating of the reaction mixture iscontinued until a sample of the reaction mixture containing 40% byweight of dissolved solids exhibits a viscosity of from 0.04 to 0.5 Pa·sat 25° C. Continuing the polymerization reaction beyond this point mayresult in excessive crosslinking of the polymer and ultimately inpremature gelation.

When the method and catalyst compositions of this invention are employedto prepare block copolymers using a hydroxyl-terminatedpolydimethylsiloxane as polydiorganosiloxane (i) and a partially orcompletely hydrolyzed phenyltrialkoxysilane as polyorganosiloxane (ii),it has been found that while both of these reactants are soluble intoluene, the resultant solutions are incompatible until they have atleast partially co-reacted to form a block copolymer. Not until thistime can a clear film be formed from the reaction mixture. By coating asample of this reaction mixture on a smooth, horizontal surface such asa glass microscope slide, evaporating volatile materials at ambient orelevated temperatures and observing the clarity of the resultant film,it is possible to determine whether the reaction has progressedsufficiently to form a block copolymer. Once a clear film is obtained,it is usually advantageous to continue heating the reaction mixture foran additional one to three hours. This is usually sufficient to increasethe physical properties of the cured copolymer to the level required formost end use applications.

The products of the present method are heat curable hydroxylatedorganosiloxane homopolymers and copolymers. These products are useful ascoating materials or for other applications which advantageously utilizethe unique properties of polyorganosiloxanes. These applications arethoroughly discussed in the prior art pertaining to polyorganosiloxanes.

If it is desired to store a solution containing a hydroxylatedpolyorganosiloxane prepared using the present catalyst compositions fora period of time longer than about 24 hours under ambient conditionsprior to curing it, or to concentrate the solution by distilling off aportion of the volatile materials, it is usually desirable to add astabilizer for the purpose of inhibiting subsequent gelation of thepolymer. Suitable stabilizers include the chromium, cobalt, zinc, andrare earth salts of carboxylic acids containing from 4 to 12 or morecarbon atoms.

The chromium, zinc, and cobalt salts of octanoic acid are preferredstabilizers and are typically employed at concentrations of from 1 toabout 50 ppm based on the weight of polyorganosiloxane. Atconcentrations above about 50 ppm, the stabilizers may function ascatalysts for premature curing of the polymer.

The hydroxyl-containing polyorganosiloxanes prepared using the methodand catalyst compositions of this invention can be resinous orelastomeric. The elongation and other physical properties whichdistinguish elastomeric from resinous polyorganosiloxanes aredetermined, at least in part, by the average degree of polymerization ofthe polymer molecules, the nature of hydrocarbon groups bonded tosilicon, and the extent to which the polymer is crosslinked. Forexample, block copolymers containing more than about 80 mol % ofdimethylsiloxane blocks exhibiting an average degree of polymerizationgreater than about 200 and a relatively low degree of crosslinkingexhibit values of elongation and tensile strength that are typical ofelastomeric polydimethylsiloxanes. By comparison, a copolymer containingless than 60 mol % of relatively low molecular weight dimethylsiloxaneblocks in combination with blocks formed from a hydroxylatedpolysiloxane containing silicon-bonded phenyl groups would, for thepurpose of this invention, be considered a resin, in that therecoverable elongation of the cured polymer would be less than 150% andthe tensile strength would be greater than about 2.5 megapascals (MPa).

The hydroxylated polyorganosiloxanes prepared using the catalystcompositions of this invention can be cured by heating them attemperatures of from 30° to 200° C. in the presence of catalysts whichpromote the condensation of silicon-bonded hydroxyl groups. Usefulcatalysts for this reaction are discussed in the aforementioned U.S.Pat. No. 3,308,208, which is hereby incorporated in its entirety byreference.

When hydroxylated polyorganosiloxanes are reacted under anhydrousconditions with at least an equivalent amount of at least onemonoorganotrifunctional silane containing three alkoxy, acetoxy orketoxime groups per molecule, the resultant products are curable atambient temperature in the presence of atmospheric moisture. For thepurpose of discussing curing of polyorganosiloxanes, "equivalent" isdefined as one molecule of silane for each hydroxyl group present on thepolyorganosiloxane.

The monoorganotrifunctional silanes can be represented by the generalformula R⁶ SiY₃ where R⁶ represents a monovalent hydrocarbon radical andY represents an alkoxy, acetoxy or ketoxime group. Silanes correspondingto this formula are known compounds, as are room temperature curablereaction products of these silanes with hydroxyl-containingpolyorganosiloxanes.

Typical silanes which can be reacted with the aforementionedhydroxylated polyorganosiloxanes include, for example, ketoxime silanessuch as

CH₃ Si[ON═C(CH₃)₂ ]₃, CH₃ Si[ON═C(CH₂ CH₃)(CH₃)]₃,

CH₃ CH₂ Si[ON═C(CH₃)(CH₂ CH₃)]₃,

(CH₃)₃ CSi[ON═C(CH═CH₂)(C₆ H₅)]₃

and others disclosed in U.S. Pat. No. 3,189,576;

acetoxysilanes such as methyltriacetoxysilane,

ethyltriacetoxysilane, propyltriacetoxysilane,

butyltriacetoxysilane, phenyltriacetoxysilane,

pentyltriacetoxysilane, and vinyltriacetoxysilane; and

alkoxysilanes such as methyltrimethoxysilane,

ethyltrimethoxysilane, propyltrimethoxysilane,

butyltrimethoxysilane, phenyltrimethoxysilane,

pentyltrimethoxysilane, vinyltrimethoxysilane,

methyltriethoxysilane, ethyltriethoxysilane,

phenyltriethoxysilane, butyltripropoxysilane,

pentyltriisopropoxysilane, vinyltributoxysilane,

vinyltripentoxysilane, methyltripentoxysilane,

ethyltributoxysilane, methylethoxydimethoxysilane,

methylmethoxyudiethoxysilane, ethylmethoxydiethoxysilane, andphenyltripropoxysilane. Mixtures of two or more different types ofsilanes can also be used.

The catalyst compositions of this invention are useful for preparingpolyorganosiloxanes from organosiloxane reactants other than thepreferred combinations discussed in detail hereinbefore and disclosed inthe accompanying examples. The only requirement is that the reactionmixture from which the polymer is prepared contains at least oneorganosiloxane reactant containing an average of more than one,preferably at least two, silicon-bonded hydroxyl groups per molecule.The organosiloxane reactants can include two or morepolydiorganosiloxanes containing different hydrocarbyl groups bonded tosilicon. For example, one of the reactants may be a polydimethylsiloxaneand the other a polymethylphenylsiloxane or apolymethyl-3,3,3-trifluoropropylsiloxane. Alternatively, apolydiorganosiloxane (i) component can be reacted with a firstpolysiloxane (ii) containing phenylsiloxy units and a secondpolysiloxane (ii) component containing methylsiloxy units.

The following examples disclose preferred embodiments of the presentmethod and catalyst compositions and should not be interpreted aslimiting the scope of the accompanying claims. All parts and percentagesare by weight unless otherwise indicated and Ph represents the phenylradical.

EXAMPLE 1

This example describes the preparation of an organosiloxane blockcopolymer using one of the preferred catalyst compositions of thepresent invention.

A glass reactor equipped with a mechanically driven stirrer, watercooled reflux condenser and a Dean-Stark trap to divert and store aportion of the condensate returning to the reactor was charged with 375parts of a 60% solution in toluene of a partially hydrolyzedphenyltrimethoxysilane having repeating units corresponding to theaverage formula

    PhSi(OH).sub.0.48 (OCH.sub.3).sub.0.12 O.sub.1.20,

275 parts of a hydroxyl-terminated polydimethylsiloxane exhibiting aviscosity of 8×10⁻⁵ m² /s at 25° C., 905 parts of toluene, 0.29 part ofa salt solution prepared by combining equimolar amounts (as 10% byweight aqueous solutions) of tetramethylguanidine andtrifluoromethanesulfonic acid (equivalent to 58 parts of salt permillion parts of total organosiloxane reactants) and 0.17 parts of a 10%aqueous solution of trifluoromethanesulfonic acid (equivalent to 34parts of acid per million parts of organosiloxane reactants). The molarratio of dimethylsiloxane units to phenylsiloxy units in the reactionmixture was 2.3:1, respectively.

The contents of the reactor were heated at the boiling point for 61/2hours, at which time 300 parts of reaction medium were collected in theDean-Stark trap and removed together with about 7.5 parts of water thathad collected during the course of the reaction. The solids content ofthe reaction mixture was about 40% by weight. Heating was continued foran additional 51/2 hours, during which time an additional 0.4 part ofwater collected in the trap. At this time, 0.17 part of a cobalt octoatesolution in a liquid hydrocarbon containing 6% by weight of cobalt wasadded as a stabilizer to inhibit gelation of the polymer. Heating wascontinued for an additional 41/2 hours, at which time a sample of thereaction mixture formed a clear film when coated on a glass microscopeslide. The reaction mixture was then concentrated by removing 596 partsof volatile reaction medium by distillation. After being heated for atotal of 16.5 hours, the final solution contained 56% by weight ofsolids and exhibited a viscosity of 0.924 Pa·s at 25° C. When diluted toa solids content of 40% by weight, the viscosity of the aforementionedfinal solution was 0.075 Pa·s.

A room temperature curable polyorganosiloxane composition was preparedby combining 200 parts of the final polymer solution with 20 parts ofmethyltrimethoxysilane, 0.5 parts of diisopropoxybis(ethylacetoacetato)titanium and 0.25 part of a liquid hydrocarbonsolution of cobalt octoate containing 6% by weight of cobalt. Theresultant mixture was stirred briefly to obtain a homogeneouscomposition and allowed to remain in a closed container in the absenceof moisture for one week. Samples of this composition were cured byexposing a 0.06 inch (0.15 cm.)-thick layer of the composition to atemperature of 25° C. and a relative humidity of 50% for one week, atwhich time the samples exhibited a tensile strength of 4.3 megapascals(MPa) and a maximum elongation of 98%.

EXAMPLE 2

This example demonstrates the preparation of organosiloxane blockcopolymers using various amine salts in combination with eithertrifluoromethanesulfonic acid or tetrafluoroethanesulfonic acid.

Organosiloxane block copolymers were prepared as described in theforegoing Example 1 using the types and amounts of organosiloxanereactants disclosed in that example. The reaction medium was 900 partsof toluene and from 0.17 to 0.34 part of a solution of zinc octoate in aliquid hydrocarbon containing 8% by weight of zinc was used as astabilizer in place of the cobalt octoate of Example 1.

The salts were prepared by combining of 10% by weight aqueous solutionscontaining equimolar amounts of the amines and acids specified in Table1, which also lists the amount of each salt used, the type and amount ofacid that was combined with the salt to form the catalyst compositionand the tensile strength and elongation of the polymer followingconversion to a room temperature cured material using the proceduredescribed in Example 1. The titanium compound disclosed in Example 1 wasused as the curing catalyst and no cobalt octoate was added togetherwith the titanium compound.

The viscosity measurements reported in Table 1 were obtained using a 40%by weight solution of the copolymer at a temperature of 25° C.

Amines--Tetramethylguanidine (TMG) t-butylamine (TBA)

Acids--Trifluoroacetic acid (TFA) Trifluoromethanesulfonic acid (TFMS)Tetrafluoroethanesulfonic acid (TFES) Sulfuric acid (H₂ SO₄)

In a control example, trifluoroacetic acid was employed as the free acidcomponent in place of the sulfuric or fluoroalkanesulfonic acid of thepresent invention.

                                      TABLE 1                                     __________________________________________________________________________    Salt Components                                                                        Amount of Salt                                                                        Free Acid                                                                            Viscosity                                                                            Tensile Strength.sup.1                                                                 Elongation.sup.1                      Amine                                                                              Acid                                                                              (ppm).sup.2                                                                           (ppm).sup.2                                                                          Pa.s, 40% sol.                                                                       (MPa)    (%)                                   __________________________________________________________________________    TMG  TFA 172     TFMS (154)                                                                           0.106  4.4      140                                   TBA  TFMS                                                                               86     TFMS (40)                                                                            0.173  5.5       57                                   TMG  H.sub.2 SO.sub.4                                                                  171     H.sub.2 SO.sub.4 (266)                                                               0.130  3.2      107                                   TMG  TFES                                                                              114     TFES (126)                                                   Control                                                                       TMG  TFA 228     TFA (790).sup.3                                                                      0.06   4.1      153                                   __________________________________________________________________________     .sup.1 Measured following addition of from 15 to 20 parts                     methyltrimethoxysilane, from 0.4 to 0.5 parts diisopropoxy                    bis(ethylacetoacetato)titanium and curing as disclosed in Example 1. Unit     of tensile strength are megapascals (MPa).                                    .sup.2 ppm  parts of salt or acid per million parts of organosiloxane         reactants                                                                     .sup.3 Amount of trifluoroacetic acid added included 1.25 parts of a 10%      by weight aqueous solution and 0.27 part of the undiluted acid, equivalen     to a total of 0.395 parts (790 ppm) of the undiluted acid.               

The control copolymer prepared using trifluoroacetic acid in place ofthe perfluorinated alkanesulfonic acids of this invention exhibited alower viscosity value prior to reaction with the methyltrimethoxysilane.In addition, the control process required more than 20 times the amountof acid required using the trifluoromethanesulfonic acid catalyst ofExample 1, and the water which distilled during the polymerization wasvery acidic, which indicates that this catalyst would be too corrosivefor use in metal reactors.

The control process was conducted by adding 0.57 g. of a 10% aqueoussolution of trifluoroacetic acid to the initial reaction mixture. Anaddition 0.29 g. was added after 3 hours when the rate water evolutiondecreased, followed by 4-0.1 g. portions of concentrated (100%)trifluoroacetic acid during the course of the polymerization to increasethe rate of water evolution. By comparison, a neutral distillate wasproduced by the reaction mixture catalyzed using a preferred catalystcomposition, namely the combination of t-butylammoniumtrifluoromethanesulfonate and free trifluoromethanesulfonic acid. Asample of steel wool placed in the initial reaction mixture containingthis preferred catalyst did not exhibit any rust or other signs ofcorrosion following completion of the polymerization. This indicatesthat the reaction mixture will not corrode iron or steel reactors andassociated processing equipment.

EXAMPLE 3

This example demonstrates the variations in tensile strength, elongationand hardness of cured block copolymers that are achieved by varying theratio of dimethylsiloxane to phenylsiloxane units in cured blockcopolymers prepared in accordance with the method of this invention.

The polymers were prepared by charging a nitrogen-filled reactor with800 parts of toluene and the organosiloxane reactants employed inExample 1 in the amounts indicated in the following Table 2.Tetramethylguanidine trifluoromethanesulfonate was formed in-situ byadding 0.0015 part of tetramethylguanidine as a 10% by weight aqueoussolution to the initial reaction mixture, heating for one hour at theboiling point while collecting the by-product water, adding toluene asrequired to maintain a clear solution and then adding 0.006 or 0.004part of trifluoromethanesulfonic acid as a 10% aqueous solution. Theamounts of amine and acid added were equivalent to the concentrations ofsalt and free acid shown in Table 2. The concentrations are based on theweight of organosiloxane reactants.

Following addition of the trifluoromethanesulfonic acid solution thereaction mixtures were heated with removal of by-product water byazeotropic distillation until a sample of the reaction mixture formed aclear film when coated onto a glass microscope slide, and a 1/4 inch(0.6 cm)-wide strip of the cured film could be elongated to between 11/4and 11/2 times its original length without breaking. The films werecured by heating the coated glass slides on a commerciallaboratory-type, electrically heated "hot plate" for 12 minutes usingthe "medium" thermostat setting and for an additional 12 minutes usingthe "high" thermostat setting. Additional trifluoromethanesulfonic acidwas added during the polymerization reaction as required to maintainapproximately the initial reaction rate, as measured by the rate atwhich water collected in the Dean-Stark trap. Once acceptable curedfilms were obtained, as determined using the foregoing test, thereaction mixtures were stabilized using 0.03 part of solubilizedchromium octoate or cobalt octoate as the stabilizer. The stabilizer wasdissolved in a hydrocarbon solvent and contained 6% by weight of themetal. Following addition of the stabilizer, the reaction mixtures wereconcentrated by distillation of solvent and other volatile materials toachieve a solids concentration of from 50 to 54% by weight.

Room temperature curable compositions were prepared by combining thefinal reaction mixture with 6%, based on the weight of the finalreaction mixture, of methyltrimethoxysilane, 20 parts per million partsof reaction mixture of a mixture of solubilized rare earth octoates inan unspecified liquid hydrocarbon and containing 6% of rare earths, anamount of solubilized cobalt naphthenate (in a liquid hydrocarbon)equivalent to 18 ppm of cobalt and 0.12% by weight of either tetrabutyltitanate or diisopropoxy bis(ethylacetoacetato)titanium. The resultantcompositions were molded and cured as described in Example 1 and sampleswere tested for tensile strength, elongation and hardness. Hardnessmeasurements were obtained using a Shore D durometer and the proceduredescribed in ASTM test method D-1674.

                                      TABLE 2                                     __________________________________________________________________________    Sample No.      1   2   3   4   5   6                                         __________________________________________________________________________    Weight ratio of dimethylsiloxane/                                                             55/45                                                                             55/45                                                                             70/30                                                                             70/30                                                                             45/55                                                                             45/55                                     phenylsiloxane reactants                                                      Molar ratio of dimethylsiloxane/                                                              2.13/1                                                                            2.13/1                                                                            4.07/1                                                                            4.07/1                                                                            1.42/1                                                                            1.42/1                                    phenylsiloxane units                                                          Salt concentration (ppm)                                                                      59  59  54  54  59  59                                        Free acid concentration (ppm)                                                                 131 131 69  69  75  75                                        Tensile strength (MPa)                                                                        2.76                                                                              3.67                                                                              1.84                                                                              1.69                                                                              8.42                                                                              8.26                                      Elongation (%)  88  95  345 344 30  35                                        Hardness (Shore D)                                                                            30  26  14  12  34  34                                        __________________________________________________________________________     Samples 1, 3 and 5 were cured using diisopropoxy                              bis(ethylacetoacetato)titanium (0.12%); samples 2, 4 and 6 were cured         using tetrabutyl titanate (0.12%).                                       

The foregoing data demonstrate the increase in tensile strength andhardness and the decrease in elongation observed as the relativeconcentration of phenylsiloxane units in the block copolymer isincreased. The optimum combination of these properties is achieved usinga 2.13:1 molar ratio of dimethylsiloxane units to phenylsiloxane units.

EXAMPLE 4

This example demonstrates (A) the preparation of a polydimethylsiloxaneusing a preferred salt component of the present catalyst compositionsand (B) the inability of the salt alone to form a useful blockcopolymer.

(A) A reactor equipped as described in example 1 was charged with 500parts of a hydroxyl-endblocked polydimethylsiloxane having a viscosityof 8.0×10⁻⁵ m² /s at 25° C., 150 parts of toluene and 0.29 part of a 10%by weight aqueous solution of tetramethylguanidiniumtrifluoromethanesulfonate, equivalent to 58 parts of salt per millionparts of organosiloxane reactant. The resultant mixture was heated atthe boiling point for 21/2 hours with stirring, during which time 4parts of water were collected and the vortex caused by the rotatingstirrer gradually disappeared due to the increasing viscosity of thereaction mixture. At this time the reaction mixture was allowed to coolto 75° C. and 375 parts of toluene were added to the reactor. Followingan additional 2.5 hours of heating at the boiling point 0.15 part oftetramethylguanidinium trifluoromethanesulfonate (as a 10% aqueoussolution) was added to the reaction mixture and heating was continuedfor 30 minutes. The very viscous reaction mixture was cooled and dividedin half. One half was diluted with 335 parts of toluene, equivalent to asolids content of 30% by weight. This solution was heated at the boilingpoint for 1.5 hours, at which time 0.15 part of tetramethylguanidiniumtrifluoromethanesulfonate solution was added and heating was continuedfor another hour. The reaction mixture was then diluted to a solidscontent of 20% by weight using 400 parts of toluene and heated to theboiling point for an additional two hours.

The viscosity of the final 20% polymer solution was 1.05×10⁻³ m² /s at25° C. The initial polymer, without any solvent present, exhibited aviscosity of 0.08×10⁻³ m² /s at 25° C., which indicates that the presentsalts are effective catalysts for polymerizing polydimethylsiloxanes inthe absence of additional acid.

(B) An attempt was made to carry out a copolymerization as described inExample 1 using only the salt component of the disclosed catalystcomposition. The initial reaction mixture contained 368 g. of a 61%toluene solution of hydrolyzed phenyltrimethoxysilane, 275 g. of ahydroxyl endblocked polydimethylsiloxane exhibiting a viscosity of 0.4Pa·s at 25° C., 5 parts of a 10% aqueous solution oftetramethylguanidinium trifluoromethanesulfonate, and 467 parts oftoluene. The resultant reaction mixture was heated at the boiling pointfor 41/2 hours, during which time 10 parts of water collected in theDean Stark trap. At the end of this time period a sample of the reactionmixture was placed on a glass microscope slide. The sample exhibited asemi-solid polymer phase and a separate liquid phase. This indicatedthat the two reactants were not copolymerizing to form the single phasesolubilized copolymer obtained in Example 1. The salt concentration was0.5 part per 500 parts of organosiloxane reactants, or 0.1% by weight(1000 ppm), which is nearly 20 times the amount of salt employed inExample 1.

EXAMPLE 5

This example demonstrates the inability of trifluoromethanesulfonicacid, a preferred acid component of the present catalyst compositions,to form a block copolymer of as high molecular weight as can be achievedusing the combination of the acid with one of the present salts.

A glass reactor equipped as described in Example 1 was charged with 220parts of partially dried solid hydrolyzed phenyltrimethoxysilane(equivalent to 215 parts of dry solid), 285 parts of a hydroxylendblocked polydimethylsiloxane exhibiting a viscosity of 8.0×10⁻⁵ m²/s, 10 parts of deionized water, 700 parts of toluene, 130 parts ofxylene, and 0.1 part of a 10% aqueous solution oftrifluoromethanesulfonic acid. The resultant mixture was heated at theboiling point for 31/2 hours, during which time 21.5 parts of water werecollected. A film formed by coating a glass microscope slide with asample of the reaction mixture appeared acceptable. The reaction mixturewas then stabilized by adding 0.3 part of a liquid hydrocarbon solutionof chromium octoate containing 8% by weight of chromium and removing 360parts of reaction medium by distillation. A 39.7 weight % solution ofthe final polymer exhibited a viscosity of 11.5×10⁻³ Pa·s at 25° C. Theviscosity of a 40 weight % solution of the polymer prepared as describedin Example 1 using both the acid and salt components of the presentcatalysts was 75×10⁻³ Pa·s at 25° C. The amounts of water generatedduring both of the aforementioned polymerization reactions wereequivalent after compensating for the 10 parts of water added to thecontrol reaction (11.5 parts for the control compared with 8 parts forExample 1). Assuming that the ratio between the amount of watergenerated and the amount recovered in the Dean Stark trap are equivalentfor both reactions, the viscosity of the polymer produced using the acidalone should have been at least equivalent to the viscosity of thepolymer disclosed in Example 1 of this application.

The ability of trifluoromethanesulfonic acid to rapidly polymerize ahydroxyl endblocked polydimethylsiloxane was demonstrated by reacting500 parts of the polydimethylsiloxane of Example 1 as a solution in 125parts of toluene. This reaction mixture was heated to the boiling point,at which time 0.07 part of a 10% aqueous solution oftrifluoromethanesulfonic acid was added. Heating was continued for 1hour and 20 minutes, at which time 4.5 parts of water had been collectedand the reaction mixture became sufficiently viscous that it coated thewall of the reactor. The viscosity of the polymer solution was estimatedto be about 5,000 Pa·s.

EXAMPLE 6

This example demonstrates preparation of a block copolymer in accordancewith the present method using a trimethylsiloxy endblockedpolydimethylsiloxane as one of the reactants.

A block copolymer was prepared using the procedure and apparatusdescribed in Example 1. The reactor was charged with 158 parts of a 60%solution in toluene of the partially hydrolyzed phenyltrimethoxysilane,salt solution (0.29 part) and acid solution (0.17 part) described inExample 1, 500 parts of toluene and 143 parts of a trimethylsiloxyendblocked polydimethylsiloxane exhibiting a viscosity of 72 Pa·s at 25°C. The resultant mixture was heated at the boiling point for one hour,during which time 2.5 parts of water were collected. A sample from thereaction mixture formed an acceptable, clear film when placed on a glassmicroscope slide and cured as described in Example 3. At this time 250parts of reaction medium were removed by distillation, 0.17 part of asolution of zinc octoate in a liquid hydrocarbon containing 8% of zincwas added and the resultant mixture was heated to the boiling point foran additional 45 minutes, at which time 42 parts of reaction medium wereremoved by distillation. A 40% by weight solution of the reactionproduct exhibited a viscosity of 0.021 Pa·s at 25° C.

The fact that clear, cured films were formed indicated that the twosiloxane reactants had formed a copolymer. It is believed that formationof such a copolymer required hydrolysis of siloxane bonds in the initialtrimethylsiloxy endblocked polydimethylsiloxane. The resultant hydroxylendblocked molecules subsequently reacted with the hydrolyzedphenyltrimethoxysilane to form a copolymer.

That which is claimed is:
 1. A catalyst composition for preparingpolyorganosiloxanes by the reaction of at least one polyorganosiloxanecontaining a plurality of silicon-bonded hydroxyl groups, said catalystcomposition consisting essentially of (1) at least one salt derived fromequimolar amounts of an organic amine containing at least one primary,secondary or tertiary nitrogen atom and an acid selected from the groupconsisting of mono- and polyfunctional carboxylic acids, mono- andpolyfunctional organosulfonic acids, phosphoric acid and sulfuric acid,and (2) at least one unreacted acid selected from the group consistingof fluorinated alkanesulfonic acids and sulfuric acid and where theweight ratio of salt (1) to unreacted acid (2) is from 1:30 to 50:1,respectively.
 2. A composition according to claim 1 where said salt isderived from a monoalkylamine or a 1,1,3,3-tetraalkylguanidine whereinthe alkyl groups of the mono-alkylamine and tetraalkylguanidine containfrom 1 to 8 carbon atoms.
 3. A composition according to claim 2 wherethe monoalkylamine is t-butylamine and the 1,1,3,3-tetraalkylguanidineis 1,1,3,3-tetramethylguanidine.
 4. A composition according to claim 1where said salt is derived from sulfuric acid, a polyfluorinatedcarboxylic acid, or a polyfluorinated alkanesulfonic acid.
 5. Acomposition according to claim 4 where said polyfluorinated carboxylicacid is trifluoroacetic acid and the polyfluorinated alkanesulfonic acidis trifluoromethanesulfonic acid or tetrafluoroethanesulfonic acid.
 6. Acomposition according to claim 1 where said unreacted acid is sulfuricacid.
 7. A composition according to claim 1 where said unreacted acid isa fluorinated alkanesulfonic acid represented by the formula R_(f) SO₃ Hwhere R_(f) represents a perfluoroalkyl radical containing from 1 to 12carbon atoms, a H(CF₂)_(d) CF₂ radical or a F(CF₂)_(d) CFHCF₂ --radicaland d is 0, 1, or
 2. 8. A composition according to claim 7 where saidfluorinated alkanesulfonic acid is trifluoromethanesulfonic acid ortetrafluoroethanesulfonic acid.
 9. A composition according to claim 1where the weight ratio of (1) to (2) is from 1:3 to 3:1, respectively.